Back-channel-etched tft substrate and manufacturing method thereof

ABSTRACT

The invention provides a BCE TFT substrate and manufacturing method thereof. The manufacturing method of BCE TFT substrate of the invention comprises disposing the surface layer of the source and drain as a conductorized IGZO film. Because the bonding between the conductorized IGZO film and the silicon oxide is strong, the passivation layer is prevented from curling up and forming bubbles. Moreover, in the process to form the source and drain the fluorine-free etching solution is used to remove the source-drain spacer, causing no damage to the channel region of the active layer. In the BCE TFT substrate of the invention, the surface layer of the source and drain is disposed as a conductorized IGZO film. Because the bonding between the conductorized IGZO film and the silicon oxide is strong, the passivation layer is prevented from curling up and forming bubbles.

CROSS REFERENCE TO RELATED APPLICATIONS

This is a divisional application of co-pending U.S. patent applicationSer. No. 15/749,105, filed on Jan. 30, 2018, which is a national stageof PCT Application No. PCT/CN2017/117327, filed on Dec. 20, 2017,claiming foreign priority of Chinese Patent Application No.201711167386.5, filed on Nov. 21, 2017.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to the field of display techniques, and inparticular to a back-channel-etched thin film transistor (TFT) substrateand manufacturing method thereof.

2. The Related Arts

The liquid crystal display (LCD) provides advantages of thinness, lowpower-consumption and no radiation, and is widely used in, such as, LCDtelevisions, mobile phones, personal digital assistants (PDAs), digitalcameras, computer screens, laptop screens, and so on.

The organic light-emitting diode (OLED) display device, also calledorganic electroluminescent display, is a new type of panel displaydevice. Because the OLED display device provides the advantages ofsimple manufacturing process, low cost, low power consumption, highluminous efficiency, wide temperature range operation, thinness andlightness, short response time, ability to achieve color display andlarge-screen display, easy to realize matching with IC driver, and easyto realize flexible display, and is thus recognized as the mostpromising display device in the industry.

The OLED display can be classified into passive matrix OLED (PMOLED) andactive matrix OLED (AMOLED) according to the driving mode, that is, thedirect addressing and the thin film transistor (TFT) array addressingtwo categories. Among them, AMOLED has a pixel array, is an activedisplay type, high luminous efficiency, and usually used forhigh-definition large-size display device.

The thin film transistor (TFT) is the main driving element in the LCDand AMOLED display device, and is directly related to the developmenttrend of the high-performance panel display. The TFT has many types ofstructures, and can be manufactured in various materials. The amorphoussilicon (a-Si) is the more common used material.

As the LCD and AMOLED display device develop towards the large-size andhigh-resolution, the only about 1 cm²/(Vs) mobility of the conventionala-Si has been unable to meet the requirements, while the metal oxidematerial, such as, indium gallium zinc oxide (IGZO) with the more than10 cm²/(Vs) mobility, and the corresponding TFT fabricationcompatibility with existing production line of a-Si semiconductors, hasrapidly become the focus of research and development in recent years.

Compared to the conventional a-Si TFT, IGZO TFT provides the followingadvantages:

1. Improve the resolution of the display backplane: under the premise ofguaranteeing the same transmittance, IGZO TFT display backplaneresolution can be done more than 2 times of the a-Si TFT, as the carrierconcentration of IGZO material is high and the mobility is high so as toreduce the size of the TFT, to ensure resolution improvement;

2. Reduce the energy consumption of the display device: compared to a-SiTFT and LTPS TFT, the leakage current of the IGZO TFT is less than 1 pA;the driving frequency is reduced from the original 30-50 Hz to 2-5 Hz,and can even reach 1 Hz through special process. Although the number ofTFT driving times is reduced, the number still maintains the alignmentof the LC molecules without affecting the quality of the image. As such,the power consumption of the display backplane is reduced. In addition,the high mobility of the IGZO semiconductor material enables the smallersize TFTs to provide sufficient charging ability and higher capacitance,and also improves the aperture ratio of the liquid crystal panel, theeffective area of light penetration becomes larger, the same brightnesscan be achieved with fewer backplane components or low powerconsumption, and the energy consumption can be reduced;

3. by using intermittent driving, the influence of the noise of the LCDdriving circuit on the touch screen detection circuit can be reduced,the higher sensitivity can be achieved, and even the tip of theballpoint pen tip can respond. Moreover, the power can be cut off as thescreen is not updated; therefore, the performance on the energy-savingperformance is better.

Currently, the TFT with IGZO as semiconductor active layer generallyadopts an etch stop layer (ESL) structure. The ESL can effectivelyprotect the IGZO from being affected in the source-drain etchingprocess, to ensure that TFT has excellent semiconductor properties.However, the manufacturing process of IGZO TFT with ESL structure iscomplicated and requires six photolithography processes, which isdisabling for cost reduction. Therefore, the development of IGZO TFTwith a back-channel-etched (BCE) structure with less photolithographyprocesses is generally pursued.

Regardless of ESL-structured TFT or BCE-structured TFT, the metal of thesource and the drain is covered with a passivation layer (PV). Unlikea-Si TFT, the material of the passivation layer of IGZO TFT is oftenSiO_(x), and the metal for the source and the drain is Cu. Because thebonding between Cu and SiO_(x) is weak, the passivation layer thin filmon the metallic source and drain will curl up and form bubbles,resulting in poor yield rate.

SUMMARY OF THE INVENTION

The object of the present invention is to provide a manufacturing methodof the back-channel-etched (BCE) TFT substrate, able to prevent thepassivation layer from curling up and forming bubbles, while not causingdamaging to the channel region of the active layer.

Another object of the present invention is to provide a BCE TFTsubstrate, preventing the passivation layer from curling up and formingbubbles, while providing stable electric properties.

To achieve the above object, the present invention provides amanufacturing method of back-channel-etched TFT substrate, comprising:

providing a base substrate, depositing metal on the base substrate andetching the metal to form a gate, forming a gate insulating layer on thebase substrate and the gate;

forming an active layer on the gate insulating layer;

depositing a source-drain material layer on the active layer and thegate insulating layer, the source-drain material layer comprising: afirst source-drain material layer disposed on the active layer and thegate insulating layer, a second source-drain material layer disposed onthe first source-drain material, and a third source-drain material layerdisposed on the second source-drain material layer; the firstsource-drain material layer comprising Mo, the second source-drainmaterial layer comprising Cu, and the third source-drain material layerbeing a conductorized IGZO film;

defining a source-drain pattern region and a non-pattern regionsurrounding the source-drain pattern region on the source-drain materiallayer, with the source-drain pattern region comprising a sourcepredetermined pattern region, a drain predetermined pattern region, anda source-drain spacer located between the source predetermined patternregion and the drain-target pattern region;

forming a photo-resist layer on the source-drain material layer,patternizing the photo-resist layer with a half-tone mask, removing theportion of the photo-resist layer corresponding to the non-patternregion, and thinning the portion of the photo-resist layer correspondingto the source-drain spacer;

removing the non-pattern region of the source-drain material layer byusing a fluorine-containing etching solution;

performing an ashing process on remaining photo-resist layer to removethe portion of the photo-resist layer corresponding to the source-drainspacer, thinning the portions of the photo-resist layer corresponding tothe source predetermined pattern region and the drain predeterminedpattern region;

removing the source-drain spacer of the source-drain material layer byetching with a fluorine-free etchant;

stripping off remaining photo-resist layer to obtain the source anddrain disposed at intervals;

forming a passivation layer on the source, the drain, the active layerand the gate insulating layer.

According to a preferred embodiment of the present invention, theconductorized IGZO film is prepared by magnetron sputtering; during themagnetron sputtering process, oxygen is not added into the reactionchamber, and the molar ratio of indium, gallium, zinc, and oxide in theobtained IGZO film is In:Ga:Zn:O=1:1:1:X, where X is less than 4.

According to a preferred embodiment of the present invention, the gatecomprises a first gate layer disposed on the base substrate and a secondgate layer disposed on the first gate layer, the material of first gatelayer comprises Mo, and the material of the second gate layer comprisesCu.

According to a preferred embodiment of the present invention, thematerial of the active layer comprises IGZO.

According to a preferred embodiment of the present invention, thematerial of passivation layer comprises SiO_(x).

The present invention also provides a back-channel-etched TFT substrate,comprising: a base substrate, a gate disposed on the base substrate, agate insulating layer disposed on the base substrate and the gate, anactive layer disposed on the gate insulating layer, a source and a draindisposed at interval on the active layer, and a passivation layerdisposed on the source, the drain, and the active layer;

the source and the drain being formed by patternizing a source-drainmaterial layer, the source-drain material layer comprising: a firstsource-drain material layer disposed on the active layer, a secondsource-drain material layer disposed on the first source-drain material,and a third source-drain material layer disposed on the secondsource-drain material layer; the first source-drain material layercomprising Mo, the second source-drain material layer comprising Cu, andthe third source-drain material layer being a conductorized IGZO film.

According to a preferred embodiment of the present invention, the molarratio of indium, gallium, zinc, and oxide in the conductorized IGZO filmis In:Ga:Zn:O=1:1:1:X, where X is less than 4.

According to a preferred embodiment of the present invention, the gatecomprises a first gate layer disposed on the base substrate and a secondgate layer disposed on the first gate layer, the material of first gatelayer comprises Mo, and the material of the second gate layer comprisesCu.

According to a preferred embodiment of the present invention, thematerial of the active layer comprises IGZO.

According to a preferred embodiment of the present invention, thematerial of passivation layer comprises SiO_(x).

The present invention also provides a manufacturing method ofback-channel-etched TFT substrate, comprising:

providing a base substrate, depositing metal on the base substrate andetching the metal to form a gate, forming a gate insulating layer on thebase substrate and the gate;

forming an active layer on the gate insulating layer;

depositing a source-drain material layer on the active layer and thegate insulating layer, the source-drain material layer comprising: afirst source-drain material layer disposed on the active layer and thegate insulating layer, a second source-drain material layer disposed onthe first source-drain material, and a third source-drain material layerdisposed on the second source-drain material layer; the firstsource-drain material layer comprising Mo, the second source-drainmaterial layer comprising Cu, and the third source-drain material layerbeing a conductorized IGZO film;

defining a source-drain pattern region and a non-pattern regionsurrounding the source-drain pattern region on the source-drain materiallayer, with the source-drain pattern region comprising a sourcepredetermined pattern region, a drain predetermined pattern region, anda source-drain spacer located between the source predetermined patternregion and the drain-target pattern region;

forming a photo-resist layer on the source-drain material layer,patternizing the photo-resist layer with a half-tone mask, removing theportion of the photo-resist layer corresponding to the non-patternregion, and thinning the portion of the photo-resist layer correspondingto the source-drain spacer;

removing the non-pattern region of the source-drain material layer byusing a fluorine-containing etching solution;

performing an ashing process on remaining photo-resist layer to removethe portion of the photo-resist layer corresponding to the source-drainspacer, thinning the portions of the photo-resist layer corresponding tothe source predetermined pattern region and the drain predeterminedpattern region;

removing the source-drain spacer of the source-drain material layer byetching with a fluorine-free etchant;

stripping off remaining photo-resist layer to obtain the source anddrain disposed at intervals;

forming a passivation layer on the source, the drain, the active layerand the gate insulating layer;

wherein the conductorized IGZO film being prepared by magnetronsputtering; during the magnetron sputtering process, no oxygen beingadded into the reaction chamber, and the molar ratio of indium, gallium,zinc, and oxide in the obtained IGZO film being In:Ga:Zn:O=1:1:1:X,where X being less than 4;

wherein the gate comprising a first gate layer disposed on the basesubstrate and a second gate layer disposed on the first gate layer, thematerial of first gate layer comprising Mo, and the material of thesecond gate layer comprising Cu;

wherein the material of the active layer comprising IGZO;

wherein the material of the passivation layer comprising SiO_(x).

The present invention provides the following advantages. Themanufacturing method of BCE TFT substrate of the present inventioncomprises disposing the surface layer of the source and drain as aconductorized IGZO film. Because the bonding between the conductorizedIGZO film and the silicon oxide is strong, the passivation layer isprevented from curling up and forming bubbles. Moreover, in the processto form the source and drain the fluorine-free etching solution is usedto remove the source-drain spacer, causing no damage to the channelregion of the active layer. In the BCE TFT substrate of the presentinvention, the surface layer of the source and drain is disposed as aconductorized IGZO film. Because the bonding between the conductorizedIGZO film and the silicon oxide is strong, the passivation layer isprevented from curling up and forming bubbles.

BRIEF DESCRIPTION OF THE DRAWINGS

To make the technical solution of the embodiments according to thepresent invention, a brief description of the drawings that arenecessary for the illustration of the embodiments will be given asfollows. Apparently, the drawings described below show only exampleembodiments of the present invention and for those having ordinaryskills in the art, other drawings may be easily obtained from thesedrawings without paying any creative effort. In the drawings:

FIG. 1 is a schematic view showing a flowchart of the manufacturingmethod of BCE TFT substrate provided by an embodiment of the presentinvention;

FIG. 2 is a schematic view showing Step S1 of the manufacturing methodof the BCE TFT substrate provided by an embodiment of the presentinvention;

FIG. 3 is a schematic view showing Step S2 of the manufacturing methodof the BCE TFT substrate provided by an embodiment of the presentinvention;

FIG. 4 is a schematic view showing Step S3 of the manufacturing methodof the BCE TFT substrate provided by an embodiment of the presentinvention;

FIGS. 5-10 are schematic views showing Step S4 of the manufacturingmethod of the BCE TFT substrate provided by an embodiment of the presentinvention;

FIG. 11 is a schematic view showing Step S5 of the manufacturing methodof the BCE TFT substrate and the structure of the BCE TFT substrateprovided by an embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

To further explain the technique means and effect of the presentinvention, the following uses preferred embodiments and drawings fordetailed description.

Referring to FIG. 1, the present invention provides a manufacturingmethod of back-channel-etched TFT substrate, comprising:

Step S1: as shown in FIG. 2, providing a base substrate 10, depositingmetal on the base substrate 10 and etching the metal to form a gate 20,forming a gate insulating layer 30 on the base substrate 10 and the gate20.

Specifically, the gate 20 comprises a first gate layer 21 disposed onthe base substrate 10 and a second gate layer 22 disposed on the firstgate layer 21, the material of first gate layer 21 comprises Mo, and thematerial of the second gate layer 22 comprises Cu.

Step S2: as shown in FIG. 3, forming an active layer 40 on the gateinsulating layer 30.

Specifically, the material of the active layer 40 comprises IGZO.

Specifically, the active layer 40 is formed by a sputtering depositingprocess and a photo-etching patternizing process.

Step S3: as shown in FIG. 4, depositing a source-drain material layer 70on the active layer 40 and the gate insulating layer 30, thesource-drain material layer 70 comprising: a first source-drain materiallayer 41 disposed on the active layer 40 and the gate insulating layer30, a second source-drain material layer 42 disposed on the firstsource-drain material 41, and a third source-drain material layer 43disposed on the second source-drain material layer 42; the firstsource-drain material layer 41 comprising Mo, the second source-drainmaterial layer 42 comprising Cu, and the third source-drain materiallayer 43 being a conductorized IGZO film.

Specifically, the conductorized IGZO film is prepared by magnetronsputtering; during the magnetron sputtering process, oxygen is not addedinto the reaction chamber, and the molar ratio of indium, gallium, zinc,and oxide in the obtained IGZO film is In:Ga:Zn:O=1:1:1:X, where X isless than 4.

Under the normal operation in the IGZO magnetron sputtering process, thereaction chamber will be injected with oxygen to ensure that theresulting IGZO layer of indium, gallium, zinc, and oxide ratio ofIn:Ga:Zn:O=1:1:1:4, thereby ensuring IGZO film has semiconductingproperties. In the invention, the oxygen content in the conductorizedIGZO film is reduced by removing the oxygen in the reaction chamberduring the magnetron sputtering process to realize the conductorproperties.

Step S4: as shown in FIGS. 5-6, defining a source-drain pattern region71 and a non-pattern region 72 surrounding the source-drain patternregion 71 on the source-drain material layer 70, with the source-drainpattern region 71 comprising a source predetermined pattern region 711,a drain predetermined pattern region 712, and a source-drain spacer 713located between the source predetermined pattern region 711 and thedrain-target pattern region 712;

forming a photo-resist layer 80 on the source-drain material layer 70,patternizing the photo-resist layer 80 with a half-tone mask 90,removing the portion of the photo-resist layer 80 corresponding to thenon-pattern region 72, and thinning the portion of the photo-resistlayer 80 corresponding to the source-drain spacer 713;

as shown in FIG. 7, removing the non-pattern region 72 of thesource-drain material layer 70 by using a fluorine-containing etchingsolution; the fluorine-containing etching solution able to etching thethird source-drain material layer 43, the second source-drain materiallayer 42, and the first source-drain material layer 41, and thefluorine-containing etching solution having a faster etching effect onthe third source-drain material layer 43, the second source-drainmaterial layer 42, and the first source-drain material layer 41.

Specifically, the fluorine-containing etching solution is afluorine-containing acidic copper etching solution, and the specificcomposition thereof is the prior art and is not described herein.

As shown in FIG. 8, performing an ashing process on remainingphoto-resist layer 80 to remove the portion of the photo-resist layer 80corresponding to the source-drain spacer 713, thinning the portions ofthe photo-resist layer 80 corresponding to the source predeterminedpattern region 711 and the drain predetermined pattern region 712;

as shown in FIG. 9, removing the source-drain spacer 713 of thesource-drain material layer 70 by etching with a fluorine-free etchant;the fluorine-free etching solution able to etching the thirdsource-drain material layer 43, the second source-drain material layer42, and the first source-drain material layer 41, and the fluorine-freeetching solution having a faster etching effect on the secondsource-drain material layer 42, and the first source-drain materiallayer 41, and a slower etching effect on the third source-drain materiallayer 43, i.e., the fluorine-free etching solution having a sloweretching speed than the fluorine-free etching solution on the IGZO.

Because the fluorine-free etching solution having a slower etching speedon IGZO, the use of fluorine-free etching solution on the source-drainspacer 713 of the source-drain material layer 70 can ensure that thechannel region of the active layer 40 prepared with the IGZO materialwill not be damaged by controlling the etching time, leading toimprovement of TFT device stability.

Specifically, the fluorine-free etching solution is a fluorine-freeacidic copper etching solution, and the specific composition thereof isthe prior art and is not described herein.

As shown in FIG. 10, stripping off remaining photo-resist layer 80 toobtain the source 51 and drain 52 disposed at intervals.

Other metal materials, such as Ti, have been used in the presentinvention to replace the conductorized UGZO to prepare the thirdsource-drain material layer 43 to enhance the bonding strength betweenthe source 51 and the drain 52 and the SiO_(x). However, the secondsource-drain material layer 42 made of copper tends to form a solutionbattery with the third source-drain material layer 43 made of othermetal materials, resulting in an electrochemical reaction so that in theprocessing of etching the source-drain material layer 70, the thirdsource-drain material layer 43 made of other metal material is easilyetched away to cause the photo-resist layer 80 above the thirdsource-drain material layer 43 to be stripped off, resulting in thefailure of the photo-etching process of the source 51 and the drain 52.In the present invention, the IGZO material is used to prepare the thirdsource-drain electrode material layer 43 to enhance the bonding strengthbetween the source 51 and the drain 52 and the SiO_(x), the thirdsource-drain material layer 43 made of conductorized IGZO material andthe second source-drain material layer 42 made of the copper materialwill not form a solution battery, and no electrochemical reactionoccurs. Therefore, during the etching of the source-drain material layer70, the third source-drain material layer 43 will not be dissolved, andthe photo-resist layer 80 above the third source-drain material layer 43will not be stripped off.

Step S5: as shown in FIG. 11, forming a passivation layer 60 on thesource 51, the drain 52, the active layer 40 and the gate insulatinglayer 30.

Specifically, the material of passivation layer comprises SiO_(x).

Because the material of the surface layer of the source 51 and the drain52, which is the third source-drain material layer 43, is aconductorized IGZO film, the bonding strength between the conductorizedIGZO film and the silicon oxide is strong, so that the passivation layer60 is prevented from curling up and forming bubbles.

The manufacturing method of BCE TFT substrate of the present inventioncomprises disposing the surface layer of the source 51 and drain 52 as aconductorized IGZO film. Because the bonding between the conductorizedIGZO film and the silicon oxide is strong, the passivation layer 60 isprevented from curling up and forming bubbles. Moreover, in the processto form the source 51 and drain 52 the fluorine-free etching solution isused to remove the source-drain spacer, causing no damage to the channelregion of the active layer 40.

Referring to FIG. 11, and FIGS. 2-10, the present invention alsoprovides a back-channel-etched TFT substrate, comprising: a basesubstrate 10, a gate 20 disposed on the base substrate 10, a gateinsulating layer 30 disposed on the base substrate 10 and the gate 20,an active layer 40 disposed on the gate insulating layer 30, a source 51and a drain 52 disposed at interval on the active layer 40, and apassivation layer 60 disposed on the source 51, the drain 52, and theactive layer 40;

the source 51 and the drain 52 being formed by patternizing asource-drain material layer 70, the source-drain material layer 70comprising: a first source-drain material layer 41 disposed on theactive layer 40, a second source-drain material layer 42 disposed on thefirst source-drain material 41, and a third source-drain material layer43 disposed on the second source-drain material layer 42; the firstsource-drain material layer 41 comprising Mo, the second source-drainmaterial layer 42 comprising Cu, and the third source-drain materiallayer 43 being a conductorized IGZO film.

Specifically, the molar ratio of indium, gallium, zinc, and oxide in theconductorized IGZO film is In:Ga:Zn:O=1:1:1:X, where X is less than 4.

Specifically, the gate 20 comprises a first gate layer 21 disposed onthe base substrate 10 and a second gate layer 22 disposed on the firstgate layer 21, the material of first gate layer 21 comprises Mo, and thematerial of the second gate layer 22 comprises Cu.

Specifically, the material of the active layer 40 comprises IGZO.

In the BCE TFT substrate of the present invention, the surface layer ofthe source 51 and drain 52 is disposed as a conductorized IGZO film.Because the bonding between the conductorized IGZO film and the siliconoxide is strong, the passivation layer 60 is prevented from curling upand forming bubbles.

In summary, the present invention provides a BCE TFT substrate andmanufacturing method thereof. The manufacturing method of BCE TFTsubstrate of the present invention comprises disposing the surface layerof the source and drain as a conductorized IGZO film. Because thebonding between the conductorized IGZO film and the silicon oxide isstrong, the passivation layer is prevented from curling up and formingbubbles. Moreover, in the process to form the source and drain thefluorine-free etching solution is used to remove the source-drainspacer, causing no damage to the channel region of the active layer. Inthe BCE TFT substrate of the present invention, the surface layer of thesource and drain is disposed as a conductorized IGZO film. Because thebonding between the conductorized IGZO film and the silicon oxide isstrong, the passivation layer is prevented from curling up and formingbubbles.

It should be noted that in the present disclosure the terms, such as,first, second are only for distinguishing an entity or operation fromanother entity or operation, and does not imply any specific relation ororder between the entities or operations. Also, the terms “comprises”,“include”, and other similar variations, do not exclude the inclusion ofother non-listed elements. Without further restrictions, the expression“comprises a . . . ” does not exclude other identical elements frompresence besides the listed elements.

Embodiments of the present invention have been described, but notintending to impose any unduly constraint to the appended claims. Anymodification of equivalent structure or equivalent process madeaccording to the disclosure and drawings of the present invention, orany application thereof, directly or indirectly, to other related fieldsof technique, is considered encompassed in the scope of protectiondefined by the clams of the present invention.

What is claimed is:
 1. A back-channel-etched (BCE) thin film transistor(TFT) substrate, comprising: a base substrate, a gate disposed on thebase substrate, a gate insulating layer disposed on the base substrateand the gate, an active layer disposed on the gate insulating layer, asource and a drain disposed at interval on the active layer, and apassivation layer disposed on the source, the drain, and the activelayer; the source and the drain being formed by patternizing asource-drain material layer, the source-drain material layer comprising:a first source-drain material layer disposed on the active layer, asecond source-drain material layer disposed on the first source-drainmaterial, and a third source-drain material layer disposed on the secondsource-drain material layer; the first source-drain material layercomprising Mo, the second source-drain material layer comprising Cu, andthe third source-drain material layer being a conductorized IGZO film.2. The BCE TFT substrate as claimed in claim 1, wherein the molar ratioof indium, gallium, zinc, and oxide in the conductorized IGZO film isIn:Ga:Zn:O=1:1:1:X, where X is less than
 4. 3. The BCE TFT substrate asclaimed in claim 1, wherein the gate comprises a first gate layerdisposed on the base substrate and a second gate layer disposed on thefirst gate layer, the material of first gate layer comprises Mo, and thematerial of the second gate layer comprises Cu.
 4. The BCE TFT substrateas claimed in claim 1, wherein the material of the active layercomprises IGZO.
 5. The BCE TFT substrate as claimed in claim 1, whereinthe material of the passivation layer comprises SiO_(x).